The present invention relates to heating, ventilation and air conditioning systems for vehicles, and in particular to such systems having dual modes for providing heat to passenger compartments of the vehicles.
In a conventional automotive vehicle employing an internal combustion engine, the heating of the passenger compartment is accomplished by running engine coolant, typically a mix of water and glycol (antifreeze), through a heater core in the passenger compartment, and then blowing air over the heater core and onto the passengers. The drawback with this is that the heater core will not provide heat until the engine has caused the coolant to warm up. For most conventional engines, this time to warm up the coolant is sufficiently short to satisfy the vehicle passengers.
Now, however, newer engines and powertrain arrangements are being developed where the engine does not produce as much excess heat for the coolant to absorb. Some examples are a direct injection engine and a hybrid (engine/motor) powertrain. For these types of powertrains, the temperature of the coolant can take a very long time to rise to a level where it will allow for adequate heating of the passenger compartment when using a conventional heating system.
Most automotive vehicles today also include an air conditioning system for cooling the air in the passenger compartment. The air conditioning system can begin to operate almost as soon as the vehicle is started. Some, then, have recognized that the components of the air conditioning system can be employed to operate in a heat pump mode, and so the conventional coolant based heating system is replace with heat from the heat pump operation. But these systems become less and less efficient for heating as the ambient air temperature becomes colder. Consequently, they have not proven efficient enough to provide an adequate heating function to replace the current type of heating system.
Thus, it is desirable to have a vehicle heating and cooling system that overcomes the drawbacks of conventional vehicle heating, and heat pump systems in order to warm a vehicle passenger compartment more quickly.
In its embodiments, the present invention contemplates a heating and cooling system for a vehicle having an engine and a passenger compartment. The heating and cooling system includes a first coolant loop having a coolant outlet line and a coolant inlet line adapted to couple to the engine, a heater core, a first heat exchanger, and a coolant valve for selectively directing flow of a coolant from the coolant outlet line to the coolant inlet line through one of the heater core and the first heat exchanger. The system also includes a second coolant loop having a pump for selectively circulating the coolant through a first coolant/refrigerant heat exchanger, the heater core, and back to the pump. There is also a refrigerant loop having a compressor with an inlet and an outlet, a first refrigerant valve for selectively directing the flow of a refrigerant from the compressor outlet to one of a condenser and the first coolant/refrigerant heat exchanger, a refrigerant passage for directing the flow of the refrigerant through an evaporator, and a refrigerant line for returning the refrigerant to the compressor inlet.
The present invention further contemplates a method of providing heating and cooling to a passenger compartment of a vehicle having an engine, the method comprising the steps of: selectively circulating a coolant from the engine, through one of a heater core located in the passenger compartment and a first coolant/refrigerant heat exchanger, and back to the engine; selectively circulating the coolant from a pump, through a second coolant/refrigerant heat exchanger, and back to the pump; selectively circulating a refrigerant from a compressor and back to the compressor through one of a first refrigerant path, having a condenser, and evaporator, and an expansion valve between the condenser and the evaporator, and a second refrigerant path, having the second coolant/refrigerant heat exchanger, the first coolant/refrigerant heat exchanger, and the expansion valve between the second coolant/refrigerant heat exchanger and the first coolant/refrigerant heat exchanger.
An advantage of the present invention is that the vehicle heating and cooling system can operate in a conventional air conditioning mode, with cooling efficiencies essentially as good as with a conventional air conditioning system, and yet still operate in a heat pump mode to provide supplemental heating when the conventional heating system is not up to an efficient operating temperature.
Another advantage of the present invention is that, in the heat pump mode of operation, the coolant absorbs heat from the refrigerant in the heat pump system, which is more efficient than absorbing heat from the ambient air.
A further advantage of the present invention is that the heating and cooling system can operate in all three modes with a minimum of heat exchangers, valves and other system components, thus minimizing the cost of the system.